Stephen Hagiochristophorites was of humble origin. The archbishop Eustathius of Thessalonica records that his father was a tax-collector. In the second half of the reign of Manuel I Komnenos (r. 1143–1180), Hagiochristophorites tried to attach himself to the imperial court, but was confronted by the ridicule and hostility of the aristocracy. Indeed, according to Eustathius, when he attempted to seduce an aristocratic lady and take her to wife to advance his own position, he was publicly flogged and had his nose cut off. Nevertheless, his determination was rewarded, and he was able to climb the administrative hierarchy, finally culminating in the office of administrator of the army, which he apparently received by Manuel I himself and held during the short reign of his son, Alexios II Komnenos (r. 1180–1182).
Hagiochristophorites continued in this post when the rebellion of Andronikos I Komnenos brought him to the throne, an event that marked a radical change in his fortunes. Within a very short time, Hagiochristophorites established himself as the new emperor's most trusted and powerful minister. Along with
Constantine Tripsychos and
Theodore Dadibrenos, Hagiochristophorites strangled Alexios II Komnenos with a bowstring in September/October 1183, leaving Andronikos as the sole emperor, a feat for which he was rewarded with the rank of pansebastos sebastos and the post of logothetes tou dromou.
By September 1185, discontent in Constantinople was seething against Andronikos' regime: popular rumour said that a celebrated image of Saint Paul was shedding tears, and even a court soothsayer, Skleros Seth, had foretold that the name of Andronikos' successor would start with an "I". Andronikos and his followers took this to mean the young aristocrat Isaac Angelos, and on 11 September, they struck: while the emperor retired to a palace on the Asian suburbs of the city, Hagiochristophorites and his attendants went to Isaac Angelos' house near the Peribleptos Monastery. Isaac at first panicked but then resolved to go down fighting, and, wielding a sword and riding his horse, charged his assailants. Faced with this unexpected attack, Hagiochristophorites turned to flee, but Isaac struck him on the head and left him dead. After wounding the attendants and forcing them to flee, Isaac galloped down the Mese thoroughfare on horseback to the Hagia Sophia, shouting to the populace of his deed. Thus driven to an act of open sedition, and with the populace rallying behind him, on the next day Isaac was crowned emperor by the Patriarch Basil Kamateros, while Andronikos fled and was captured and executed a few days later.